iOS Views


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iOS Views

  1. 1. UIVIEW употреба, хитрости и задълженияThursday, January 5, 12
  2. 2. UIVIEW • defines a rectangular region on the screen • drawing and touch events • placement and sizing of other viewsThursday, January 5, 12
  3. 3. CONTAINER VIEW • resizing behavior Групиране • hiding a view • alpha (transparency) • mathematical transform to the coordinate system • responder chain (touches)Thursday, January 5, 12
  4. 4. UIVIEW AND CALAYER CHAPTER 1 View and Window Architecture Figure 1-1 Architecture of the views in a sample application UIView UIWindow UIImageView UIToolbar UIBarButtonItem (internal view) UIKit views Core Animation layers The use of Core Animation layer objects has important implications for performance. The actual drawing code of a view object is called as little as possible, and when the code is called, the results are cached by Core Animation and reused as much as possible later. Reusing already-‐rendered content eliminates the Всяко View е изгранено от CALayer expensive drawing cycle usually needed to update views. Reuse of this content is especially important during animations, where the existing content can be manipulated. Such reuse is much less expensive than creating new content.Thursday, January 5, 12
  5. 5. CALAYER Quartz 2D Reuse Drawing Hardware buffers Performance Render Animation Transform matricesThursday, January 5, 12
  6. 6. CHAPTER 1 CUSTOM DRAWING View and Window Architecture Figure 1-7 UIKit interactions with your view objects iPhone OS Your Application Touch Framework touches setNeedsLayout Mark redraw Touches UIKit setNeedsDisplay frame, alpha, etc. layoutSubviews • Buffers setNeedsDisplay • Images frame, alpha, etc. • Attributes • Geometry drawRect • Animations Compositor Draw images, text, etc. Graphics hardware The following steps break the event sequence in Figure 1-‐7 (page 23) down even further and explain what happens at each stage and how you might want your application to react in response. 1. The user touches the screen. 2. APPLE: Avoid custom drawing! The hardware reports the touch event to the UIKit framework. 3. The UIKit framework packages the touch into a UIEvent object and dispatches it to the appropriate view. (For a detailed explanation of how UIKit delivers events to your views, see Event Handling Guide for iOS.)Thursday, January 5, 12
  7. 7. CHAPTER 1 View and Window Architecture CHAPTER 1 Overview of Quartz 2D UIKIT Figure 1-‐4 shows this coordinate system r windows and views define their own loca to the view or window origin instead of r Figure 1-4 Coordinate system orient Figure 1-5 Quartz 2D UIKit Modifying the coordinate system creates a mirrored image. y (0,0) x (0,0) x (0,0) y x Default Coordinates Modified Coordinates • drawing - own coordinate system y • geometry changes - superview’s coordinate system. flipped_coordinates.eps Cocoa Drawing Apple Computer, Inc. February 9, 2006 Because every view and window definesThursday, January 5, 12 coordinate system is in effect at any given
  8. 8. UIVIEW АМИНАЦИИ • frame, bounds, center • transform — rotate or scale the view. • alpha • backgroundColor • contentStretch • //autoresizingMaskThursday, January 5, 12
  9. 9. FRAME & BOUNDS Frame rectangle Bounds rectangle (40,40) (0,0) Center (160,230) 380 380 240 240 coordinates in coordinates superview in selfThursday, January 5, 12
  10. 10. РАЗТЯГАНЕ НА КОНТЕНТ CHAPTER 1 View and Window Architecture Stretchable Views You can designate a portion of a view as stretchable so that when the size of the view changes only the content in the stretchable portion is affected. You typically use stretchable areas for buttons or other views where part of the view defines a repeatable pattern. The stretchable area you specify can allow for stretching Core Animation layer along one or both axes of the view. Of course, when stretching a view along two axes, the edges of the view must also define a repeatable pattern to avoid any distortion. Figure 1-‐3 shows how this distortion manifests stretchable area - contentStretch property itself in a view. The color from each of the view’s original pixels is replicated to fill the corresponding area in the larger view. Figure 1-3 Stretching the background of a button (0,0) (1,1) UIViewContentModeScaleToFill UIViewContentModeScaleAspectFit UIViewContentModeScaleAspectFill You specify the stretchable area of a view using the contentStretch property. This property accepts a rectangle whose values are normalized to the range 0.0 to 1.0. When stretching the view, the system multiplies these normalized values by the view’s current bounds and scale factor to determine which pixel or pixels need to be stretched. The use of normalized values alleviates the need for you to update the contentStretch property every time the bounds of your view change. The view’s content mode also plays a role in determining how the view’s stretchable area is used. Stretchable areas are only used when the content mode would cause the view’s content to be scaled. This means that stretchable views are supported only with the UIViewContentModeScaleToFill, UIViewContentModeScaleAspectFit, and UIViewContentModeScaleAspectFill content modes. IfThursday, January 5, 12
  11. 11. ПРИМЕРИThursday, January 5, 12
  12. 12. РЕЦИКЛИРАНЕ НА КОНТЕНТ Първоначално Bitmap изобразяване Render contentThursday, January 5, 12
  13. 13. TOUCHES User input Touch Framework UIKit UIEvent UIView UIView UIView (superview) (superview) Responder chainThursday, January 5, 12
  14. 14. PERFORMANCE • ViewControllers - колко и за какво се използват • Избягвайте да чертаете сами • Използвайте contentModes & AutoResizingMask • aView.opaque = YES; когато е възможно • Scrolling optimisationThursday, January 5, 12
  15. 15. CUSTOM VIEWS • initWithFrame: Не забравяй! • dealloc • autoresizingMask • addGestureRecognizer: or touchesBegan:withEvent:Thursday, January 5, 12
  16. 16. APPENDIX A The iOS Environment APPLICATION SANDBOX Figure A-1 Sandbox directories in iOS App Sandbox Documents App Library ... tmp ... App Sandbox App ... App Sandbox App ... Important: The purpose of a sandbox is to limit the damage that a compromised app can cause to the system. Sandboxes do not prevent attacks from happening to a particular app and it is still your responsibility to code defensively to prevent attacks. For example, if your app does not validate user input and there is an exploitable buffer overflow in your input-‐handling code, an attacker could still hijack your app or cause it to crash. The sandbox only prevents the hijacked app from affecting other apps and other parts of the system.Thursday, January 5, 12